In the field of naval warfare, there is a need to neutralize mines moored underwater. The present invention fulfills this need.
The role of mines in naval warfare is well-known. For example, during World War I, mines were laid by the Turks in the Dardanelles to frustrate an Allied fleet seeking to pass through that strait to attack Constantinople. The presence of these mines, the inability of the attacking Allied fleet to remove them, and the sinking by mines of some Allied warships in an area (Eren Kui Bay) previously thought neutralized, led to the bloody but unsuccessful invasion of the inhospitable Gallipoli peninsula. More recently, during Operation Desert Storm, mines damaged USS Princeton and USS Tripoli.
One type of mine that is deployed in water is the moored mine, also known as a tethered mine. Such mines generally consist of a buoyant explosives package having appropriate detonator(s), an anchor, and a mooring cable or chain (also called a mooring or a tether) which connects the two. The mooring tethers the mine so that the mine is suspended at some depth. Moored mines commonly have a clump anchor and a mooring that are deployed from a floodable housing at the bottom end of the mine. The mine is kept submerged to reduce its detectability, but is kept close enough to the surface of the water to substantially damage or destroy a surface vessel or a submerged vessel that causes the mine to detonate. The mine detonation may be caused by physical contact by magnetism of the vessel's steel hull, by acoustic noise from propellers, and by pressure. Some mines use a variety of triggers, and can discriminate between levels of the above factors (e.g. due to desired size of the target vessel). Obviously, the mooring is held substantially vertically (subject to currents and other factors) between the anchor and the explosives package. Such mines can be deployed or sown from a surface vessel or a submarine, or can be dropped from aircraft.
In the prior art, moored mines would be removed by a variety of means, but commonly by a specialized ship called a minesweeper, which is constructed of materials that would not cause, or would at least substantially reduce the likelihood of, actuating a mine's magnetic trigger that could detonate the explosives package of the mine. Such a ship would tow a sweep wire at a depth at which the mine mooring would be expected to be present. Alternatively, the wire sweep can instead be towed by a helicopter, which can arrive at a mined location several miles distant faster than can a ship. One such helicopter-towed sweep wire arrangement is illustrated at FIGS. 1 and 2 of U.S. Pat. No. 4,020,780 issued May 3, 1977 to Richard K. Shumaker et al., which is hereby incorporated by reference herein. A diverted sweep wire array armed with cutters is used to sweep moored mines. Each wire is diverted to one side. A depressor is used to maintain the wires at a desired depth. The sweep wire is used to cut the mooring, causing the mine to rise to the surface for neutralization, e.g. destruction. Gunfire is generally used for this purpose. Unfortunately, the released mines while floating on the surface are generally sufficiently small that, especially in the presence of sea waves or darkness, they are difficult to visually detect and destroy.
Conventional minesweeping only cuts the mooring. The freed mine floats to the surface where it is commonly neutralized by gunfire, usually requiring a second vessel. Presently, conventional minesweeping can therefore only be performed during periods of good visibility, a severe tactical limitation. Floating mines that escape neutralization present a danger to the minesweeper(s) and other marine assets. If the mine mooring is not severed, the mine will likely be pulled down and over the sweep wire. This presents a serious problem to the minesweeper and its crew when the conventional sweep gear is recovered.
The minesweeper generally has a wood or fiberglass hull. The minesweeper has on its stern winch(es) of a non-magnetic material from which one or more non-magnetic cables are deployed. Such cables, called sweep wires, are towed behind the minessweep in a combined inverted single or full V configuration. Along the weep wire are located a series of mooring cutters. This V shape may be about 100 yards across at its rear. The sweep wires are held below the water surface by a depressor wire provided with one or more depressors, and is held relatively horizontal in the water by devices called otters, assisted by one or more floats which are usually at the free ends of the sweep wires to mark their location. A paravane can be used to divert each wire to port or starboard of the tow. Each sweep wire can be two or more wires, each towed behind and to one side (port or starboard) of the minesweeper to together form an inverted V shape. Disposed along the length of the sweep wire at regular intervals are mooring cutters. One such cutter employed by the U.S. Navy is called "Cutter, Powder Activated, Minesweeping Mark 17 Mod. 1". This cutter has a chisel with a 44 magnum shotgun shell or similar and a small trip wire. When the mine mooring comes up against the trip wire, it releases a trigger which fires the shotgun shell to propel the chisel out and cut the mooring, thereby releasing the mine to float up to the surface. Other cutters were coated with particles of diamond or had sharpened files for sawing at the mine mooring. Such cutters are described in U.S. Pat. No. 3,844,244 issued Oct. 29, 1974 to William B. White, and in U.S. Pat. No. 4,120,246 issued Oct. 17, 1978 to Udo Sabranski et al., which are each hereby incorporated by reference herein. If a moored mine is encountered, then as the sweep wire is pulled through the water, the mine mooring runs along the sweep wire until a cutter is encountered which cuts the mooring. Such sweep apparatus is described in U.S. Navy Mine Countermeasures Familiarizer produced by the Naval Mine Warfare Engineering Activity, Yorktown, Va. (October 1991) which is hereby incorporated by reference herein.
One problem that has been encountered with cutters is that of marine growth. This marine growth can be seaweed, stringy or large leaf grass, or calcareous. Such growth can foul a cutter.
When a cutter cuts the mine tether, the mine floats up to the surface. Usually another vessel neutralizes the mine, with gunfire, such as from 50 caliber machine guns, when the minesweeper is well away. Thus, two vessels are commonly used for this purpose. Thus, minesweeping is dangerous in bad weather, and extremely difficult if not impossible at night. If the floating mine is exploded when the sweep gear is nearby, the sweep gear could be destroyed or disturbed sufficiently that sweeping operations would have to be stopped and repairs or readjustments made. If the mine case is penetrated, then the mine will flood and sink. If the charge or the detonator of the mine are not neutralized, then when the minesweep crew retrieves their sweep gear, they may find a live mine therein, obviously an undesirable situation.
It is also desirable that mines sown by friendly forces, such to impede movement of enemy vessels, evade such sweep efforts. The passthrough mechanism of the present invention also fulfills this need.